`forward_event`
A notification for topic `forward_event` is sent every time the status
of a forward payment is set. The json format is same as the API
`listforwards`.
```json
{
"forward_event": {
"payment_hash": "f5a6a059a25d1e329d9b094aeeec8c2191ca037d3f5b0662e21ae850debe8ea2",
"in_channel": "103x2x1",
"out_channel": "103x1x1",
"in_msatoshi": 100001001,
"in_msat": "100001001msat",
"out_msatoshi": 100000000,
"out_msat": "100000000msat",
"fee": 1001,
"fee_msat": "1001msat",
"status": "settled",
"received_time": 1560696342.368,
"resolved_time": 1560696342.556
}
}
```
or
```json
{
"forward_event": {
"payment_hash": "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
"in_channel": "103x2x1",
"out_channel": "110x1x0",
"in_msatoshi": 100001001,
"in_msat": "100001001msat",
"out_msatoshi": 100000000,
"out_msat": "100000000msat",
"fee": 1001,
"fee_msat": "1001msat",
"status": "local_failed",
"failcode": 16392,
"failreason": "WIRE_PERMANENT_CHANNEL_FAILURE",
"received_time": 1560696343.052
}
}
```
- The status includes `offered`, `settled`, `failed` and `local_failed`,
and they are all string type in json.
- When the forward payment is valid for us, we'll set `offered`
and send the forward payment to next hop to resolve;
- When the payment forwarded by us gets paid eventually, the forward
payment will change the status from `offered` to `settled`;
- If payment fails locally(like failing to resolve locally) or the
corresponding htlc with next hop fails(like htlc timeout), we will
set the status as `local_failed`. `local_failed` may be set before
setting `offered` or after setting `offered`. In fact, from the
time we receive the htlc of the previous hop, all we can know the
cause of the failure is treated as `local_failed`. `local_failed`
only occuors locally or happens in the htlc between us and next hop;
- If `local_failed` is set before `offered`, this
means we just received htlc from the previous hop and haven't
generate htlc for next hop. In this case, the json of `forward_event`
sets the fields of `out_msatoshi`, `out_msat`,`fee` and `out_channel`
as 0;
- Note: In fact, for this case we may be not sure if this incoming
htlc represents a pay to us or a payment we need to forward.
We just simply treat all incoming failed to resolve as
`local_failed`.
- Only in `local_failed` case, json includes `failcode` and
`failreason` fields;
- `failed` means the payment forwarded by us fails in the
latter hops, and the failure isn't related to us, so we aren't
accessed to the fail reason. `failed` must be set after
`offered`.
- `failed` case doesn't include `failcode` and `failreason`
fields;
- `received_time` means when we received the htlc of this payment from
the previous peer. It will be contained into all status case;
- `resolved_time` means when the htlc of this payment between us and the
next peer was resolved. The resolved result may success or fail, so
only `settled` and `failed` case contain `resolved_time`;
- The `failcode` and `failreason` are defined in [BOLT 4][bolt4-failure-codes].
This notification bases on `LOG_BROKEN` and `LOG_UNUSUAL` level log.
--Introduction
A notification for topic `warning` is sent every time a new `BROKEN`/
`UNUSUAL` level(in plugins, we use `error`/`warn`) log generated, which
means an unusual/borken thing happens, such as channel failed,
message resolving failed...
```json
{
"warning": {
"level": "warn",
"time": "1559743608.565342521",
"source": "lightningd(17652): 0821f80652fb840239df8dc99205792bba2e559a05469915804c08420230e23c7c chan #7854:",
"log": "Peer permanent failure in CHANNELD_NORMAL: lightning_channeld: sent ERROR bad reestablish dataloss msg"
}
}
```
1. `level` is `warn` or `error`:
`warn` means something seems bad happened and it's under control, but
we'd better check it;
`error` means something extremely bad is out of control, and it may lead
to crash;
2. `time` is the second since epoch;
3. `source`, in fact, is the `prefix` of the log_entry. It means where
the event happened, it may have the following forms:
`<node_id> chan #<db_id_of_channel>:`, `lightningd(<lightningd_pid>):`,
`plugin-<plugin_name>:`, `<daemon_name>(<daemon_pid>):`, `jsonrpc:`,
`jcon fd <error_fd_to_jsonrpc>:`, `plugin-manager`;
4. `log` is the context of the original log entry.
--Note:
1. The main code uses `UNUSUAL`/`BROKEN`, and plugin module uses `warn`
/`error`, considering the consistency with plugin, warning choose `warn`
/`error`. But users who use c-lightning with plugins may want to
`getlog` with specified level when receive warning. It's the duty for
plugin dev to turn `warn`/`error` into `UNUSUAL`/`BROKEN` and present it
to the users, or pass it directly to `getlog`;
2. About time, `json_log()` in `log` module uses the Relative Time, from
the time when `log_book` inited to the time when this event happend.
But I consider the `UNUSUAL`/`BROKEN` event is rare, and it is very
likely to happen after running for a long time, so for users, they will
pay more attention to Absolute Time.
-- Related Change
1. Remove the definitions of `log`, `log_book`, `log_entry` from `log.c`
to `log.h`, then they can be used in warning declaration and definition.
2. Remove `void json_add_time(struct json_stream *result, const char
*fieldname, struct timespec ts)` from `log.c` to `json.c`, and add
related declaration in `json.h`. Now the notification function in
`notification.c` can call it.
2. Add a pointer to `struct lightningd` in `struct log_book`. This may
affect the independence of the `log` module, but storing a pointer to
`ld` is more direct;
I tried to just do gossipd, but it was uncontainable, so this ended up being
a complete sweep.
We didn't get much space saving in gossipd, even though we should save
24 bytes per node.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
